This invention relates to furnace roof jacks, and, more particularly, to a furnace roof jack which is provided with a pivoting flashing plate.
Sealed combustion forced air furnaces conventionally use of roof jack assembly for supplying combustion air and for exhausting flue gases. The roof jack assembly extends upwardly from the furnace through the roof of the dwelling and includes an inner tube for exhausting flue gases and an outer tube for supplying outside air for combustion.
Sealed combustion furnaces are commonly used in mobile homes or manufactured housing. Mobile homes are usually provided with a very tight, sealed construction, and all of the air for combustion in the furnace must be obtained from outside the home.
Conventional roof jacks consist of two concentric tubes. The inner tube provides a passage for flue gases to the outside, and the outer tube provides a path for combustion air from the outside to the furnace burner. The upper ends of the inner and outer tubes terminate above the roof line of the home and are protected by rain caps.
In the conventional manufactured housing application, the roof is relatively horizontal and a roof flashing or rain plate is welded to the outside of the jack in a plane which is perpendicular to the axis of the jack. Sealant is applied to the lower face of the flange, and the jack is inserted through a suitably sized hole in the roof until the flashing contacts the roof surface. The lower end of the jack is pulled down and attached to the furnace top, and sheet metal screws are driven through the flange into the roof to complete the installation. The flashing is supported by the roof and supports the upper section of the jack.
In the case of homes with pitched roofs, a wedge shaped spacer of suitable dimensions must be installed between the roof flashing and the roof to allow proper installation. The extra part adds to cost, increases the number of joints which must be sealed against the weather, and requires stocking of various wedge sizes and pitches to accommodate the various possible roof pitches.